1. Field of the Invention
This application relates to cleaning a substrate, such as a semiconductor wafer. More specifically, this application provides methods and apparatus for processing a substrate in a cleaning and/or surface preparation process.
2. Description of the Related Art
Substrate surface preparation and cleaning is an essential step in the semiconductor manufacturing process. Multiple cleaning steps can be performed on one or a plurality of substrates. The process recipe may include etch, clean, rinse, and dry steps, which, in combination, and may be referred to generally as a substrate surface cleaning/surface preparation process. The substrate or substrates are exposed to a variety of process and rinse chemicals in chambers configured for a single substrate or more than one substrate, or multiple chambers configured for a single substrate or more than one substrate. Process chemicals include etchants, for example acids such as hydrofluoric acid (HF), hydrochloric acid (HCl), among others, rinsing agents, such as de-ionized (DI) water, and cleaning agents, such as standard clean 1 (SC1) and/or an ammonia/peroxide mixture (APM). Each cleaning chamber may have piezoelectric transducers to propagate megasonic energy into the chamber's cleaning solution, which enhances cleaning by inducing microcavitation in the cleaning solution helping to dislodge particles off of the substrate surface. Drying of the substrate or substrates is also performed and may be facilitated by using a rinse/drying solution, such as isopropyl alcohol (IPA) among other fluids.
The chemicals typically used in common semiconductor surface cleaning/surface preparation processes require strict safety and disposal standards due to the harmful nature of some of the chemicals. Each chemical has a threshold limit value (TLV®) that reflects the level of exposure that the typical worker can experience without an unreasonable risk of disease or injury when he/she interacts with the vapors emitted during the cleaning process. Also, in some cleaning processes, flammable materials are used. To facilitate safe operation, the cleaning chamber or chambers are typically isolated from the clean room environment by the use of a containment vessel or cabinet. To prevent safety hazards, such as fire or explosions or chemical exposure, one may need to exhaust the emitted vapors to assure that concentration of vapors in the containment vessel is low enough, for example, below the lower explosion limit (LEL). To facilitate removal of the vapors, the containment vessel may be coupled to a source of negative pressure to remove harmful vapors so that the vapors in the containment vessel will not cause a safety hazard, such as a fire or explosion or exposure to personnel.
Due to various hardware and processing constraints the containment vessel or cabinet is typically much larger than the cleaning vessel. Additionally, in some conventional systems, each cleaning chamber may be coupled to a source of negative pressure to facilitate removal of vapors emitted by that chamber. The large vessel may also include a volume that requires a high volume exhaust source in order to efficiently and/or sufficiently remove the vapors and fumes. However, some vapors may escape the cleaning chamber and fill the containment vessel, which may create the safety hazards mentioned above. Further, if the vapors or fumes are not removed sufficiently, the large containment vessel can create a safety hazard by pockets or areas of high vapor concentration. Therefore, there is need to assure that a worker's exposure to the harmful vapors when he/she interacts with the cleaning chamber or containment vessel is below the TLV® for that particular chemical, and to minimize accumulation of volatile vapors exterior to the cleaning chamber.
What is needed is an apparatus and method of containing substantially all vapors from an individual chamber within the processing system in order to minimize or eliminate the safety concerns mentioned above.